Reactions of sodium with hydrocarbons



Patented Nov. 5, 1935 REACTIONS OF SODIUM WITH HYDROCARBONS Norman D.Scott, Niagara Falls, N. Y assignor to E. 1. du Pont de Nemours &Company, Inc., Wilmington, DeL, a corporation of Delaware No Drawing.Application September 29, 1933 a Serial No. 691,574

14 Claims. (01. 260-168) cally to a method of effecting addition ofalkali 5 metals to naphthalene and its homologues. This application is acontinuation in part of my copending application, Serial No. 638,524,filed 0ctober 19, 1932.

It is well known that alkali metals will react with a wide variety ofhydrocarbons under a wide variety of conditions. An extensive review ofthis work has been published by C. B. Wooster, ,1 Chemical Reviews XI 1Aug. 1932). While most of the reactions described are at present oflittle technical significance on account of the cost of the materialsinvolved, thereis particular interest in the attempts that have beenmade to react alkali metals with the cheaper aromatic hydrocarbons suchas naphthalene. Schlenk (Annalen 463 95) carried out slow reactionsusing lithium in ethyl ether and obtained sufllcient reaction in eightdays with naphthalene, and in fourteen days with diphenyl, to permitsome examination of the products formed. He represented the alkali metalcompounds by the formulae,

Schlenk, using ethyl ether as solvent, failed to get any detectablereaction of sodium with these hydrocarbons even in months. He attributedthis to a'poisoning efiect on the sodium of minute traces-of sulfurcompounds present even in the best grades of naphthalene as supplied fora standard for calorimetry.

The reaction of sodium with naphthalene has also been studied to someextent using liquid ammonia as solvent. At ordinary temperatures, thereaction'products are sodamide and tetralin. At low temperatures a .redsolution is obtained which has been shown by Wooster (J. A. C. S. 53179-187 1931), to be in all probability a monosodium tetralin formed byaddition of four atoms of sodium to one molecule of naphthalene,followed by imm'ediate ammonolysis of three atoms of the sodium tosodamide as represented by the equations:

CioHsNiu+3NHa=3NaNH2+C1oH 1Na Because of the large consumption of sodiumand reactivity of the ammonia used as solvent, this method ispractically useless as a means of preparing acids or other derivativesfrom naph-- thalene. An object of this invention is to provide a 5method for causing alkali metalsv and specifically sodium, to be addedto naphthalene: further object is to cause this reaction to be carriedout at temperatures and under conditions favorable to the stability of,the products; a further object is 10 to provide a rapid reaction; myinvention also includes the product or products formed by the additionof sodium andpotassium tofnaphthalene. Other objects will appear fromthe description of the invention.

I have found that certain solvents and classes of solvents have a veryspecific action in promoting the reaction of alkali metals withnaphthalene to form addition, products. As stated, the action of thesesolvents is specific, but I do not know whether their action iscatalytic, whether the solvent itself takes part in the reaction in somemanner, or whether there are some solubility or other physical factorsinvolved. I

The solvents which I have found of such re- 25 markable activity andusefulness for these reactions are broadly in the class of aliphaticethers although all of these ethers are not effective, and of theeffective ones, some are better than others. Thus I have usedsatisfactorily aliphatic mono 30 ethers such as dimethyl ether, methylethyl ether,

' methyl normal propyl ether, methyl isopropyl and mixtures of thesewith other solvents. I have also tried other aliphatic mono ethers whichwould not permit this reaction to proceed, or in which the reactions areexceedingly slow, and which did not have the specific effective actionof these above mentioned, for example, diethyl ether, methyl normalbutyl ether, di isopropyl ether, methyl phenyl ether, methyl benzylether. These last mentioned ethers are without detectable eifect in theaddition of sodium to naphthalene, and. as noted, there has been foundan ex-. ceedingly slight action with lithium on naphthalene in diethylether. These ethers, however, are 45 outside of the scope of myinvention since they do not have the specific accelerating action of myefiective or active aliphatic mono ethers first above given. 7 I

, In general the mono ethers which are effective in promoting thereaction of alkali metals with napthalene or its homologues may becharacterized as aliphatic ethers containing a CHa-O group and in whichthe number of oxygen atoms and the number of carbon atoms are in a ratio5 of not less than 1:4. In the phrase oxygencarbon ratio of not lessthan 1:4 as used in the specification and claims, the ratio of 1:4refers to the ratio of the number of oxygen atoms to the number ofcarbon atoms present in the ether.

Within the restrictions above given as to the limitations of the monoethers applicable to effect these reactions these ethers mustfurthermore not be split by the alkali metal or the alkali metaladdition compounds under the conditions used. I do not mean by this thatthe ethers may not react in some way in some reversible reaction withthe alkali metal and/or naphthalene since indications are that theethers in effecting the reactions may to some extent take part in thereaction, but the ether must not be broken up or form irreversiblereaction products. Thus, for example, ethylene oxide may be considered acyclic ether falling within the limitations given for oxygen-carbonratio; however, it reacts with sodium naphthalene and hence cannotsatisfactorily perform the function required. There may be very slowether cleavage with some good solvents, but at a rate much slower thanthat of the desired reaction. In order to simplify the wording later Ifurther specify such ethers as are effective? within my invention asbeing stable" although as noted they may play some reactive role incausing the reactions to proceed.

I have found that inert non-ether types of solvents such as hydrocarbonsor alkyl sulfides which do not react with the alkali metals and which inthemselves are non-effective for the reactions may be used as dilutingagents for the effective mono ethers. There is, however, a minimumconcentration of the effective ether in the non-effective solventsbeyond which the reaction will not proceed. Thus, in general theeffective dimethyl ether can be diluted with a non-reactive,non-effective hydrocarbon up to four or five times its volume. If thedilution be as high as six times the volume of the dimethyl ether thereaction will not proceed. With the higher mono ethers, which arenon-effective in themselves, the dilution may be greater. Thus diethylether, which is not effective for the reactions, can be used in amountsup to ten times the volume of the effective dimethyl ether and thereaction of sodium and naphthalene will still proceed.

I have discovered that alkali metals can be added not only tonaphthalene but to various homologues of naphthalene by the method of myinvention. For further description, the invention will be illustratedparticularly with respect to the reaction of napthalene with sodium, butit is to be understood that what is said thereon will apply equally wellto the reaction of the other alkali metals and to any of the naphthalenehomologues capable of forming addition compounds with alkali metal.

I have found that sodium reacts very readily with naphthalene indimethyl ether solution even at 70 C. Naphthalene also reacts readilywith sodium using methyl-ethyl-ether as solvent. Other mixed mono etherswith one methyl and one higher primary aL-zyl group can also be used.The ease with which the reaction starts and the solubility of theaddition compounds decreases, however, with increasing weight of thealkyl group. With mixed methyl ethers of butyl or higher alkyls it isnecessary to add a small amount of an effective methyl ether to startthe reaction,

as the reaction appears to be very definitely autocatalytic when oncestarted.

It is to be understood also that this invention I have furtherdiscovered that a solution of naphthalene in an effective" ether willreadily dissolve sodium in an amount equivalent to one gram atom ofsodium for each gram molecule of naphthalene; thereafter the solution offurther amounts of sodium becomes so slow as to be negligible. This issomewhat unexpected sincethe reaction products obtained by furthertreatment of the sodium-naphthalene compound, for example, with water orCO: indicate that it is in 20 large part the 1,4 disodium naphthalene:

HNR

It is probable that this is an equilibrium reaction. It is also foundthat other isomeric disodium addition compounds are formed as evidencedby the formation of isomeric acids.

In view of the fact that the solution which is thus prepared, andcontains one gram atom of sodium for each gram molecule of naphthalene,is a highly colored green solution and readily conducts'an electriccurrent, it is possible that the compound may exist in solution as afree radical which may be represented by the formula:

II Na The soluble addition compound may involve the combination ofdisodium naphthalene with an extra molecule of naphthalene in some othermanner. Thus its formula could be written:

without specifying the exact method of combination. Moreover thissoluble addition product may conceivably also include some combinationwith the ether solvent to account for the specific action of theeffective aliphatic mono ethers. The reactions of this material,however, are clearly evident and I do not desire to be limited by anyhypothesis as to the probable structure in solution.

If such a solution which contains. sodium equivalent to one gram atom ofsodium for each gram molecule of naphthalene be treated with water oralcohol, it will yield equivalent amounts of naphthalene anddihydronaphthalene; with CD: it will yield the sodium salts ofdihydronaphthalene-dicarboxy acids, along with an equivalent amount ofnaphthalene. If, however, either the hydrolysis or the carboxylation iscarried out gradually while further -amounts of sodium are .present inthe liquid, further amounts of this sodium will dissolve as that in thesolution is used by the hydrolysis or carboxylation. In this manner havebeenv able: to. react essentially all of the .naph'thaleneand; recoverthe major amount as thejdihydronaphthalene. or dihydronaphthae ess c a'As dicatedabovaI-have 'made'this'additionof to naphthalene itselfr'andto its homologues such asalphaand beta methyl naphthalene. I

have found that in iithe case of naphthalene itself. the .product formedis'in large part the 1,4' disodium compound. Formation of this compoundis probably permitted by the splitting of the double bonds betweenthelz2 and 3:4 positions permit addition in a similar manner in the caseof substituted naphthalene where the 1:4 positions may be occupied byconstituent groups since the reaction is not dependent on replacement ofhydrogen or substituents by the sodium; there is no hydrogen evolvedinthe reaction of my invention as far as I have been able to discover.

I have discovered that this sodium naphthalene addition product is avery reactive material. Thus, as indicated above, hydrolysis can be madeto take place to form dihydronaphthalene, or the 7 addition productstill in the ether solution can be treated with C02 and converted intosodium salts of dihydronaphthalene-dicarboxylic acids, which can beisolated. The further reactions of this sodium naphthalene additionproduct are not, however, claimed in this application, but are thesubject matter of co-pending applications and applications to be filedat a later date.

In carrying out these reactions, I have found it to be of importance tohave the surfaces of the sodium clean. Thus the solvent must be purl--fled of such materials aswill react with sodium and tend to forminsoluble'coatings thereon, un-

der the. conditions to be used, and the sodium should be protected fromcontact with such 'reactive materials from the time it is mechanical lysubdivided. Extreme fineness of sodium is not required although the ratewill be dependent,

among other things, on the extent of sodium sur- .face, and this affordsone means of controlling the rate. [The naphthalene need not be of extreme purity. Technical flake naphthalene works quite satisfactorily;The complete absence of all sulfur compounds is not essential as shownby the fact that dimethyl sulfide can be used as an inert diluentsolvent in the effective reaction medium for thereaction of sodium withnaphthalene. The presence of free CO2 dissolved in the solvent is likelytointerfere with the reaction of sodium with naphthalene startingbecause of coating the sodium.

n the other hand, when the reaction is well started, dry CO2 can then beintroduced and the carhoxylation carried on simultaneously as long ascare is taken that the rate is insuflicient to de- .stroy completely allthe green color of the sodium naphthalene compound, which will continueto be formed by the reaction of additional sodium. In this way thepreparation of the sodium salts of the dicarboxy acids can be carriedout simultaneously in a single vessel. In order to insure completefreedom from metallic sodium in the product, however, it is better tofilter the green solution of the sodium naphthalene away from unreactedsodium and treat it with CO: in a separate vessel. This precipitates thesodium salts which can be filtered out and the solvent, together withunreacted naphthalene and a small amount of the sodium naphthalenecompound rei amounts.

turned to the first vessel. Such aproces's be timely. v v

The concentration of naphthalene or its derivatives that canbe .used is'limited only by its .5

solubility. The reaction temperaturecan'vary from at least 80 C, toabove the Imelting'point. of sodium, limited only by the stability ofthe combination of materialsused and that-of the product. The reactionsin general are fast up 10 to the solution of one gram atom of sodium pergram molecule of naphthalene in solution. In these reactions, both inthe prior reaction with sodium and in the carboxylation,-obviouslypressures above atmospheric may be used if .desired or 400 c. c. ofliquid dimethyl ether 'were placedv in a flask and maintained at orjustbelowf its boiling point at atmospheric pressure. To this was added30.5'gms. of flake naphthalene and then 11.3 gms. of clean, finelydivided sodium. The reactioncomme'nced immediately on adding the sodium,as was evidenced by,the solution turning an intensely green color. Thissolution was agitated-continuously for about fifteen min utes and then aslow stream of CO2 was introduced; this stream of CO2 was maintained atsuch rate that the greencolor of the solution was not completelydischarged until the sodium had essentially all dissolved or reacted.Toward the end of two hours the carboxylation was allowed to go tocompletion, giving a white slurry of sodium salts of dihydronaphthalenedicarboxylic acids. By treating the salts'with' aqueous HCl and repeatedextraction with ether, a total yield 40 of 87% of theory of a mixture ofthe isomeric dibasic acids was isolated. The reactions are'presumed tobe essentially quantitative, although a portion of the acid is diiiicultto extract from water. It is found that a considerable portion of theisomeric acids was the 1:4 acid. If carboxylation is carried out at lowtemperatures, 60 C. to '80 0.; higher yields of the 1:4 acid have beenobtained. Other crystalltzable acids are obtained in varying amounts,amongst which v the 1:2 acid has been found in considerable.

Example II The reaction of 2 gms. potassium with 6 gms. naphthalene wascarried out in 400 c. 0. methyl ether at -25 C. The reaction occurred atabout the same rate as sodium, but there was evidence of a side reactionprobably involving impurities in the methyl ether. tion of a whiteprecipitate even before CO2 was introduced, and a corresponding decreasein the yield of dicarboxylic acids obtained.

Example III 5 A small amount of finely divided sodium, and ofnaphthalene were placed in a test tube filled with nitrogen and a fewcubic centimeters of purified methyl isopropyl ether distilled in. 7There was no immediate formation of colored compounds, but on standingovernight there was definite formation of a yellowish green materialpartly dissolved. The greenish color was intensified by warming to theboiling point. 75

operated either as a batcn rocess} or-contlnf v f 1 This resulted in theforma- 60 Example IV 76 c. c. of methyl normal butyl ether containingExample V 11.5 gms. sodium and 39 gms. naphthalene were added to 100 c.c. 01' methyl ethyl ether. Reaction began at once. After treatment withC02, a gross yield oi! 63% of the theoretical amount ofdihydronaphthalene dicarboxylic acids was isolated from the sodiumsalts. The remainder represented mainly unreacted napthalene and sodium.

Example VI Example VII 5.8 gms. of sodium and 19 gms. of naphthalene 35were added to 100 c. c. of xylene. No colored compounds formed at roomtemperature or down to --35 C. Methyl ether was added in smallincrements. No color formed after 18 c. c. has been added, but did formwith a total of 23 c. c. of di- 40 methyl ether. Treatment with CO2after 3 hours gave sodium salts from which were isolated 1.7 gms. 01'organic acids. The colored sodium compound did not appear to be verysoluble in this solvent. 45 I claim! 1. Method of eifecting the additionof an alkali metal to an aromatic hydrocarbon of the group consisting ofnaphthalene and its alkyl derivatives which comprises bringing thealkali metal 50 and the hydrocarbon together in a reaction me-' 60 andthe hydrocarbon together in a reaction medium comprising an amountsumcient to promote the reaction of a stable aliphatic mono ether havingan oxygen to carbon ratio of not less .than 1:4 and in k which there, isa CHa-'Ogroup. I w 3. Method of eflecting the addition 01' to anaromatic hydrocarbon oi the group 5 sis ting oi naphthalene auditsalkyl'derivatives which comprises bringing and the hy-,

drocarbon together in a reaction-medium com-ff prising an amountsuillcierit to promote'the re-- action'oi a stable aliphatic mono etherhaving o an oxygen to carbon ratio of not less than 1:4.

sodium and naphthalene together in a reactionfls medium comprising anamount sufllcient to promote the reaction 0! a stablmaliph'atic monoether having an oxygen to carbon ratio '01 not 1 less than '1:4 and inwhich there 'is a CHa-O-grOilp. 20

5. Method of eflecting the addition '0! sodium to methyl naphthalenewhich comprises bring ing the sodium and naphthalene together in areaction medium comprising an amount sumcient to promote the reaction ofa mono ether 25 having an oxygen to carbon ratio or not less than 1:4and in which there is a CHz-O-grotip.

6. A sodium' addition product of naphthalene.

'7. As a new composition of matter, disodium naphthalene.

8. As a new composition of matter 1,2-diso dium naphthalene. 9. As a newcomposition of matter 1,4 disodium naphthalene. x f

10. A reactive ether solution oi. an organometallic compound comprisinga solution of an alkali metal addition to a compound of the groupconsisting of naphthalene and its alkyl derivatives in a solventcomprising an amount sumcient' to promote the reaction of a stablealiphatic 4o mono ether having an oxygen to carbon ratio or not lessthan 1:4 andin which there is a Cram-group. v 11.A reactive ethersolution'oi an organometallic compound comprising a solution of a alkylderivatives in a solvent comprising an amount sufficient to promote .thereaction of a stable aliphatic mono ether having an oxygen to carbonratio of not lessthan 1:4 and in which there is a CHz-O-QTOUP.

- 12. A solution of a sodium-naphthalene addition product in a stablealiphatic mono ether having an oxygen to carbon ratio or not less than1:4 and having a CHa-O-g'lOllD.

13. A solution of 1,4 disodium naphthalene in dimethyl ether.

14. A solution of 1,2 disodium naphthalene in dimethyl ether. 00

NORMAN D. sco'rr.

